Phospholipase A2 (PLA2) is an ubiquitous protein that is found in every cell where it has been sought. This enzyme catalyzes the hydrolysis of the sn-2- acyl position of phospholipids. Phospholipase A2 is an important enzyme. The free fatty acid which is released upon hydrolysis of the phospholipid is further metabolized into various biological agents such as leukotriences and prostaglandins. The activity of PLA2 has been implemented in various inflammatory as for example, asthma and arthritis. Information on the chemistry of how these enzymes function would be useful for both the pharmacological and medical fields. This information could aid in the design of specific drugs. The catalytic mechanism for the bovine pancreas PLA 2 has been postulated for the calcium dependent enzyme. However, the kinetic analysis of the human calcium dependent and calcium- independent PLA2's has not been reported. We propose to study and compare the substrate specificity and structural relatedness of the calcium - dependent and the calcium- independent PLA2's from human placenta. In addition, we plan to determine the effect of selected inhibitors on these phospholipases. Our aim is to better characterize the enzyme which would lead to future studies so as to better define their physiological function.